The invention concerns the use of a composition or premix based on volatile corrosion inhibitors for limiting to a maximum the degradation or release of volatile corrosion inhibitors during the preparation of the said composition.
It also concerns a composition or premix based on volatile corrosion inhibitors.
It furthermore concerns articles based on polymers and of which one of the components consists of this composition or premix, as well as the method for preparing these articles which comprise in particular packaging films, packages constructed from sheets and other parts based on polymers.
It also concerns articles in the form of pasty solids based on structuring agents and of which one of the components consists of the said composition or premix.
It finally concerns the use of the abovementioned composition and articles for the protection of metal parts against corrosion.
The use of volatile corrosion inhibitors is known when metal parts which are sensitive to corrosion are to be protected, in particular those which are made of mild steel with a low carbon content and which, once machined, are despatched as they are to their destination by maritime container with a view to their being finished on site, in particular by painting. The risks of corrosion are then considerable, especially when the parts in question are dispatched to hot and humid areas.
Volatile corrosion inhibitors offer very good protection against corrosion under these conditions and have the advantage of making it possible to avoid having to use conventional techniques for protecting metal parts; these conventional techniques consist of applying paints, varnishes, plastics, waxes, greases and oils which have to be removed before finishing on site, which leads to additional costs and pollution.
Volatile corrosion inhibitors, generally denoted by VCI, employ additives of which the vapour pressure may be considered appreciable at the temperature of use (for example of the order of 10xe2x88x925 to 10xe2x88x921 mm Hg at 20xc2x0 C.) and which are capable of inhibiting the corrosion of metals.
These VCIs act by virtue of the fact that they are conveyed in vapour form to the metal surface to be protected, to be absorbed thereon or even dissolved in any condensation water.
Products are also known which are classified in a wider sense as VCIs by the fact that one of their reaction products has an adequate vapour pressure. Accordingly, for example, sodium nitrite, in the presence of ammonium ions, can form ammonium nitrite which is relatively volatile. The original sodium nitrite is then considered as a VCI.
The use of a mixture of different products classified in a wider sense as VCIs in an inert liquid vehicle is recommended in order to obtain an optimum anticorrosive effect whatever the composition of the material to be protected (BE 702592).
When the metal parts to be protected are packaged inside films, the VCIs are incorporated in the material constituting these films, and given that these films may be situated in direct contact with the surface of the products to be protected, corrosion inhibitors acting by contact are also incorporated in the mass constituting these films.
The advantages of this protective technique by means of packaging in a film containing VCIs, lie in its great ease of application and the overall protection provided, given that the vapours penetrate into the most inaccessible places of parts with complex forms without it being necessary to resort to cleaning or previous preparation, any de-protection operation and any pollution being moreover eliminated.
It is sometimes necessary to protect against corrosion only portions of large metal parts having a complex geometry. Pasty solids formed by the normal techniques of the polymer industry (moulding, modelling, extrusion) provide metal parts with the necessary localized protection, considerably minimizing costs.
In order to incorporate VCIs in the mass constituting films or other packaging articles which are often based on thermoplastic polymers, it is known to produce direct mixtures of VCI powders with polymers and to form packaging films or solid parts such as sheets directly by extrusion or blowing.
At the extrusion temperature, which is approximately 160xc2x0 C. for low density polyethylene and 240xc2x0 C. for polypropylene, VCIs have an extremely high volatility which leads, in the case of the manufacture of a film, to the appearance of a high porosity and a high risk of degradation and/or decomposition with elimination of at least part of the VCIs. The efficiency of such films from the anticorrosion point of view is thus greatly reduced following the loss of active materials.
In order to overcome this disadvantage, i.e. in order to limit the loss of VCI during the actual preparation of the finished articles, it has been proposed to use premixes containing VCIs, i.e. concentrates of active material dispersed in supports such as polymers, solvents and plasticizers. Premixes based on polymers (Patent BR-A-9001035) have the general advantage of being homogeneous and easy to handle; these premixes are then incorporated in the polymers with a view to preparing packaging articles.
Given however, that the temperatures employed when premixes are prepared are often above 150xc2x0 C., at least partial degradation of the said premixes is observed and thus, as an example, it is noted that dicyclohexylamine nitrite, mixed and extruded with polyethylene at 160xc2x0 C., results in granules of premix which have a dark yellow coloration, characteristic of a high degree of degradation i.e. a loss of activity.
In order to prevent this excessive degradation by heat, it has been proposed to use liquid premixes, based on oil, which do not need high temperatures during their manufacture (U.S. Pat. No. 4,913,874).
However, given that VCIs are not frequently soluble in these oily media, a heterogeneity of the premix results, as well as the appearance of difficulties due to local excess or reduced concentrations when they are subsequently incorporated in polymers from which the final articles are made.
It has also been proposed to overcome this disadvantage by using liquid premixes in the form of solvent-containing or oily solutions containing VCIs, premixes which are not incorporated during extrusion but are applied onto these films by spraying, forming in this way, after the evaporation of the solvent, either a powdered VCI layer (patent DE 3 417 149 A1), or an oily layer containing the VCIs (patent GB 2 188 274 A).
The disadvantage of these premixes lies in the fact that the VCIs are not imprisoned in a matrix to give a slow release, so that the protection obtained is of short duration. In addition, the adhesion of the layers deposited on the articles is low and leads to losses during handling and the need to clean the parts which have to be protected, which is precisely what one wishes to avoid.
The object of the invention is especially to overcome the disadvantages of the previous techniques and to provide compositions based on VCI, responding better to the various practical requirements than those which already exist. Its objective is also to provide finished articles employing at least one composition based on VCI according to the invention.
The object of the invention is finally to provide novel uses for these compositions based on VCI, such as the partial and localized protection of certain large metal parts having complex forms.
In addition, it is to the credit of the Applicant Company that it has found, following in-depth research, that these objectives were achieved as soon as structuring agents were incorporated in a composition based on volatile corrosion inhibitors, said structuring agents being capable of enabling a premix to be prepared at sufficiently low temperatures so as to limit to a maximum the release and/or degradation of VCIs during this preparation.
Consequently, the object of the invention is the use of a composition or premix based on volatile corrosion inhibitors which includes, in order to limit to a maximum the release and/or degradation of VCIs when the composition or premix is formed, either an effective quantity of a structuring agent, consisting of at least one solid or pasty substance of which the melting point is 40 to 110xc2x0 C., preferably from 50 to 90xc2x0 C., or a liquid substance capable of forming, when mixed with a mineral filler, a pasty or solid whole.
According to one advantageous embodiment, in the use according to the invention, the composition comprises 1 to 90%, preferably 20 to 60% by weight of at least one volatile corrosion inhibitor and 10 to 99%, preferably 40 to 80%, of at least one of the structuring agents defined above.
According to another advantageous embodiment, in the use according to the invention, the composition includes at least one structuring agent chosen from the group of those comprising solid or pasty aliphatic and/or resinous compounds with a low melting point of between 40 and 110xc2x0 C., preferably between 50 and 90xc2x0 C.
According to another advantageous embodiment of the use according to the invention, the structuring agent of the composition is chosen from the group comprising linear and/or only slightly branched mono- or polyfunctional aliphatic organic compounds with hydrocarbon chains having at least 10 carbon atoms, including in particular:
saturated or unsaturated, possibly oxidized, mono- or dicarboxylic acids, their esters and their salts,
phosphoric, sulfonic and phosphoric acids, their esters with alcohols and their salts of alkali metals, alkaline earths, zinc, aluminium and/or organic amines,
cyclic or acyclic compounds of the group comprising lactones, ketones, aldehydes, amides and acetals,
cyclic or acyclic, possibly polyalkoxylated, primary or secondary higher alcohols with a hydrocarbon chain having at least 10 carbon atoms,
linear and/or only slightly branched aliphatic hydrocarbons, in particular paraffins and isoparaffins,
polyolefins and their copolymers with low molecular masses of 3000 to 20000 g/mole,
polyglycols, in particular polyethyleneglycols with a molecular mass of 2000 to 10000 g/mole.
According to another advantageous embodiment of the use according to the invention, the structuring agent of the composition is chosen from the group comprising resinous compounds having a polymeric and/or cyclic structure and which may contain aromatic derivatives and cyclic terptenes in a minor proportion.
According to another advantageous embodiment of the use according to the invention, the structuring agent of the composition is chosen from the group of those identified in Table A below and of which some are waxes of natural or synthetic origin.
The invention also concerns a composition or premix based on volatile corrosion inhibitors, characterized in that it includes an effective quantity of at least one structuring agent consisting of a solid substance of which the melting point is 40 to 110xc2x0 C., preferably 50 to 90xc2x0 C., by means of which the release and/or degradation of volatile corrosion inhibitors is limited to a maximum when the composition or premix is formed.
According to one advantageous embodiment, the composition according to the invention comprises 1 to 90%, preferably 20 to 60% by weight of at least one volatile corrosion inhibitor and 10 to 99%, preferably 40 to 80% of at least one structuring agent consisting of a solid substance of which the melting point is 40 to 110xc2x0 C., preferably 50 to 90xc2x0 C.
According to another advantageous embodiment, the composition according to the invention includes at least one structuring agent chosen from the group of those comprising solid aliphatic and/or resinous compounds with a low melting point of between 40 and 110xc2x0 C., preferably between 50 and 90xc2x0 C.
According to another advantageous embodiment of the composition according to the invention, the solid structuring agent is chosen from the group comprising linear and/or only slightly branched mono- or polyfunctional aliphatic organic compounds with hydrocarbon chains having at least 10 carbon atoms, including in particular:
saturated or unsaturated, possibly oxidized, mono- or dicarboxylic acids, their esters and their salts,
phosphoric, sulfonic and phosphonic acids, their esters with alcohols and their salts of alkali metals, alkaline earths, zinc, aluminium and/or organic amines,
cyclic or acyclic compounds of the group comprising lactones, ketones, aldehydes, amides and acetals,
cyclic or acyclic, possibly polyalkoxylated, primary or secondary higher alcohols with a hydrocarbon chain having at least 10 carbon atoms,
linear and/or only slightly branched aliphatic hydrocarbons, in particular paraffins and isoparaffins,
polyolefins and their copolymers with low molecular masses of 3000 to 20000 g/mole,
polyglycols, in particular polyethyleneglycols with a molecular mass of 2000 to 10000 g/mole.
According to another advantageous embodiment of the composition according to the invention, the solid structuring agent is chosen from the group comprising resinous compounds having a polymeric and/or cyclic structure and which may contain, in a minor proportion, aromatic derivatives and cyclic terpenes.
According to another advantageous embodiment, the composition according to the invention and the composition used according to the invention include at least one volatile corrosion inhibitor chosen from the group comprising:
nitrogen-containing derivatives and in particular, on the one hand, aliphatic, aromatic, acyclic or cyclic amines, including dicyclohexylamine, cyclohexylamine, morpholine, diisopropylamine and benzylamine, their organic salts, including benzoates, carbamates, laurates, caprylates, succinates or their inorganic salts including nitrites, nitrates, carbonates, phosphates, phosphites and, on the other hand, heterocyclic compounds including imidazole and its derivatives, triazoles and their derivatives, as well as hexamethylenetetramine,
oxido nitrogen-containing derivatives including the alkali metal or alkaline earth salts of nitrous acid and
the benzoic derivatives of these metals such as sodium benzoate.
It is possible to include in the composition used according to the invention or in the composition and/or finished articles according to the invention, one or more additives chosen from the group comprising:
antioxidant agents and/or degradation inhibitors including bisphenol A, butylhydroxytoluene, di-tert-butylphosphite, trinonylphenoxyphosphite, dilaurylthiodipropionate,
anti-UV absorbing agents including benzotriazoles, triazines, hydroxybenzophenones, and radical inhibitors including SHAs or Steric Hindrance Amines and HALS or Hindered Amine Light Stabilizers,
external antistatic agents including the phosphoric ethers of ethoxylated alcohols and ethoxylated amine chlorides, or internal antistatic agents including ethoxylated fatty amines, ethoxylated polyols and alkylsulfonates,
external or internal lubricating agents including paraffins, fatty alcohols, fatty acids, esters of fatty acids and alcohols and amides,
plasticizing agents including dioctylphthalate, tricresylphosphate, the diesters of aliphatic acids,
inorganic pigments including PbSO4, PbCrO4, CdS. ZnS, and organic pigments including azo, phthalocyanin or anthraquinone derivatives and
fire retardants including the brominated and chlorinated compounds of phosphorus, the hydrides of compounds of Al, Mg and Zn, as well as epoxy oligomers,
mineral fillers including chalks and carbonates, talcs, clays and silicas.
These additives may also be added only at the moment when the composition is incorporated in the polymer from which the articles according to the invention are manufactured, or in the structuring agent.
These articles are characterized in that at least one of their components consists of a composition according to the invention or in that they use a composition according to the invention, and in that they are prepared, according to a first possibility, from at least one polymer which enters into their constitution to the extent of at least 50% by weight
The abovementioned polymers which enter into the constitution of packagings and/or articles to the extent of at least 50% by mass, may be chosen from those of the group comprising:
polyolefins, including polyethylenes, polypropylene, polybutene and their copolymers with one or more unsaturated monomers including vinyl acetate, acrylic acid and its esters with alcohols having a short carbon chain,
polyvinyl chloride and its copolymers, acrylic copolymers and their derivatives, and polyamides, polystyrenes, polycarbonates, polyesters, polyurethanes, rubbers including natural rubber, styrene-butadiene and polychloroprene.
These finished articles, into the constitution of which the composition according to the invention enters, or which use a composition according to the invention, comprise not only flexible or rigid films, which are possibly retractable, but also other elements including in particular wires, tubes which are possibly formed and sheets which are possibly cellular, from which it is possible to produce packaging including a more or less sealed cavity filled with a confined atmosphere containing VCIs coming from the composition or premix, and it is within this cavity that the metal parts to be protected against corrosion are placed.
These packages may consist of single films but also of assemblies of several of the abovementioned elements, these assemblies being produced by employing any suitable method, including stapling, crimping, thermoforming, skin-packing or the manufacture of blisters.
The previously mentioned sheets may be obtained from two films according to the invention, while leaving a space between these films, it being possible for this space to be in the form of cells, or a corrugated network obtained from a third film, the assembly having the appearance of a corrugated cardboard.
The packages made from the said sheets may have channels for communication between the inside of the cavity delimited by the package and the outside, these channels having a diameter generally less than a millimetre, allowing in this way only a limited flow of air.
The communicating channels in question are established at the time when the packagings including the composition according to the invention are manufactured, or subsequently.
According to a second possibility and more precisely in the case where protection of only a portion of the metal part against corrosion is to be ensured, the article concerned by the invention is essentially based on the composition according to the invention or on the composition used according to the invention, including modelling or moulding pastes and mastics, the article thus constituted having, by virtue of its plastic character, the advantage of easy handling, and the possibility of producing at the last moment the form best suited to the geometry of the portion to be protected.
It will be recalled that mastics comprise polymers and that the modelling pastes that are free from polymers contain insoluble fillers such as the abovementioned mineral fillers.
The method for preparing these articles generally comprises successively a step for preparing a composition or premix according to the invention and a subsequent step during which the premix is incorporated in one of the abovementioned polymers, the actual packagings and articles being obtained, in particular by extrusion or blowing or by injection from the mixture comprising the premix and the polymer.
Alternatively, and in the case of pasty premixes not including polymers requiring heating during manufacture, this method may be carried out in a single step, these articles being obtained by mixing operations specific to the use of single- or two-component mastics and pasty solids.
The articles in question are used for protecting metal parts sensitive to corrosion during their transport or storage, without a complementary protective treatment being applied to these parts.
The invention will be even better understood with the aid of the following non-limiting examples which concern advantageous embodiments.